scikit-learn/scikit-learn — pull request #3986 by amueller (2014-12-19 16:52:53+00:00)
Title: MRG FIX backward compatibility.

``force_arrays`` was never in a release, ``allow_nd`` was a legal option to ``train_test_split`` that raises an error in master.

Apparently I messed this up when I did the input validation refactoring.